Comparison of coherent anti-Stokes Raman-scattering thermometry with thermocouple measurements and model predictions in both natural-gas and coal-dust flames

Mobile coherent anti-Stokes Raman-scattering equipment was applied for single-shot temperature measurements in a pilot-scale furnace with a thermal power of 300 kW, fueled with either natural gas or coal dust. Average temperatures deduced from N₂ coherent anti-Stokes Raman-scattering spectra were compared with thermocouple readings for identical flame conditions. There were evident differences between the results of both techniques, mainly in the case of the natural-gas flame. For the coal-dust flame, a strong influence of an incoherent and a coherent background, which led to remarkable changes in the spectral shape of the N₂ Q-branch spectra, was observed. Therefore an algorithm had to be developed to correct the coal-dust flame spectra before evaluation. The measured temperature profiles at two different planes in the furnace were compared with model calculations.